Intelligence and developmental instruments: standardization, norms and the right test for the age

Transcript

RyanFrance, the early 1900s. The French government has a practical problem: which children might have difficulty in school? And it asks a researcher named Alfred Binet to build a test to find out.

SoheeAnd more than a century later, the descendants of that test are still on psychologists' shelves, and on your exam.

RyanWelcome to EPPP Prep, the podcast. I'm Ryan.

SoheeI'm Sohee. Today, intelligence and developmental instruments. Where they came from, what standardization and norms really mean, and how to pick the right test for the person in front of you.

RyanBack to Binet. OpenStax says his test included many verbally based tasks. Then Louis Terman, a Stanford professor, modified it by standardizing how it was given, and tested thousands of children of different ages to establish an average score for each age.

SoheeThat became the Stanford-Binet Intelligence Scale, and an updated version is still widely used today.

RyanAnd the history has a dark side the textbook doesn't hide. IQ tests were sometimes used to support the eugenics movement. In Buck versus Bell, the Supreme Court legalized the forced sterilization of some people judged feeble-minded through this kind of testing, resulting in about 65,000 sterilizations.

SoheeWhich is part of why access is controlled today. OpenStax notes that only professionals trained in psychology can administer IQ tests, and buying most tests requires an advanced degree in psychology.

RyanTwo words from that story are core psychometrics, and they often get blurred together, so let's slow down. Standardization means the manner of administration, scoring, and interpretation of results is consistent.

SoheeNorming means giving a test to a large population so you can collect data comparing groups, such as age groups. The resulting norms are the reference scores you use to interpret future scores.

RyanAnd here's a line from the textbook I really like. Norms are not expectations of what a group should know. They're a demonstration of what that group does know.

SoheeFor norms to mean anything, the sample has to be a representative sample, a subset of the population that accurately represents the general population. The textbook's example: if you measure height only in your own class, and the basketball team happens to be taking it together, your sample won't represent typical heights.

RyanNow the IQ scale itself. On most IQ tests, the mean is 100, and in modern IQ testing one standard deviation is 15 points. So a score of 85 is one standard deviation below the mean.

SoheeScores between 85 and 115, within one standard deviation either side, are considered average, and about 68 percent of people score in that range. A score of 130 or above is considered superior.

RyanNext, the Wechsler scales. In 1939, David Wechsler, who spent part of his career working with World War One veterans, combined subtests tapping verbal and nonverbal skills into the Wechsler-Bellevue Intelligence Scale. It later became the Wechsler Adult Intelligence Scale.

SoheeToday there are three main Wechsler tests, matched to age. The Wechsler Preschool and Primary Scale of Intelligence, the WPPSI. The Wechsler Intelligence Scale for Children, the WISC. And the Wechsler Adult Intelligence Scale, the WAIS. Together they cover from age two and a half to 90.

RyanThe exact edges are worth memorizing. Yu and colleagues give the WPPSI's range as 2 years 6 months to 7 years 7 months. The WISC runs from 6 years to 16 years 11 months.

SoheeNotice the overlap at ages 6 and 7. In our practice items, the age always falls clearly inside one range.

RyanAnd their reliability is well documented. Yu's team reports acceptable to good internal consistency reliability for these scales, for example point seven seven to point nine three for the WISC-V, and test-retest reliability for the WISC-V from point eight to point nine one.

RyanIn the current WISC, the fifth edition, the subtests make up five indices: Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing Speed. You get a score for each index and a Full Scale IQ.

SoheeThen there's a fourth Wechsler test that trips people up: the Wechsler Abbreviated Scale of Intelligence, Second Edition, the WASI-II. It covers ages 6 to 90. But it's abbreviated.

RyanYu's team says it includes only the verbal comprehension and perceptual reasoning composites, and gives an estimated IQ score, rather than a comprehensive IQ. About 30 minutes.

SoheeLet's pause and think. A school psychologist is evaluating a 9-year-old for a possible learning disability. The team needs a comprehensive IQ score plus separate scores for verbal comprehension, visual-spatial skills, working memory, fluid reasoning and processing speed. A teacher suggests a shorter test to save time. What's the right instrument?

RyanThe WISC-V. Nine is inside its age range, and it gives a comprehensive IQ with all five index scores. The shorter test, the WASI-II, would only give an estimate, with two composites.

SoheeAnd the other wrong answers are age mismatches. The WPPSI is for young children, and the WAIS is the adult version.

RyanHere's a subtle point about appropriate use with various populations. Yu's team notes that autistic individuals were included in the standardization samples for the WPPSI and the WISC, but not for the WASI-II. So who's in the norm group can matter for who you're testing.

SoheeNorms also age. OpenStax says the Wechsler tests are periodically normed and standardized again as a way of recalibrating. Children taking the WISC-V today are compared with their same-age peers from a national sample of thousands.

RyanAnd those recalibrations revealed the Flynn effect: each generation scoring significantly higher on IQ tests than the last. Flynn himself argued that this doesn't necessarily mean younger generations are more intelligent.

SoheeAnd the textbook is candid that how valid intelligence tests are is still debated. Which skills to assess, how well any test can truly measure intelligence, and how the results get used.

RyanOne example from the courts: in 2014, in Hall versus Florida, the Supreme Court ruled that IQ scores can't be used as a final determination of a prisoner's eligibility for the death penalty.

SoheeWhich brings us to what an IQ score doesn't capture: everyday functioning. Yu's team describes adaptive behavior as conceptual, social and practical skills, like understanding money and time, getting along with others, personal care and safety.

RyanAnd assessing adaptive behavior helps determine strengths and challenges, inform treatment goals, and track response to intervention. For autistic individuals, the Vineland Adaptive Behavior Scales are one of the two most commonly used instruments, with forms that gather information from parents and teachers, across the lifespan, from birth to age 90.

SoheeLet's round out the toolkit with autism instruments, since they show how screening and diagnosis use different tools. The Modified Checklist for Autism in Toddlers, revised with follow-up, is one of the most widely used first-level screeners, a two-stage screener for toddlers ages 16 to 30 months.

RyanThe Social Communication Questionnaire is a 40-item yes-or-no caregiver rating scale, used as a second-level screener for children older than 4 with a mental age above 2.

SoheeAnd for diagnosis, the Autism Diagnostic Observation Schedule is considered the gold-standard semi-structured, interaction-based observational evaluation for autism.

RyanSecond pause and think. A juvenile court orders a comprehensive intellectual evaluation of a 14-year-old to guide decisions about services. The evaluator needs a full IQ score and the complete set of index scores, not an estimate. Which test?

SoheeThe WISC. Fourteen is within 6 to 16, and it gives a comprehensive IQ with the full index profile. The abbreviated scale gives only an estimate.

RyanAnd if that same court had asked about a 20-year-old, you'd move up to the adult scale. Age first, then purpose: a full profile, or a quick estimate.

RyanLet's recap. Standardization: consistent administration, scoring and interpretation. Norming: testing a large, representative sample to create reference scores. Norms show what a group does know, not what it should.

SoheeIQ: mean 100, standard deviation 15, about 68 percent between 85 and 115.

RyanWechsler by age: WPPSI from 2 and a half to about 7 and a half. WISC from 6 through 16. WAIS for adults. The WASI-II is brief, ages 6 to 90, with an estimated IQ.

SoheeAdaptive behavior measures, like the Vineland, show everyday functioning that an IQ score can't. And screening tools and diagnostic tools are different instruments with different jobs.

RyanIf you've ever been anxious about being reduced to a number yourself, this episode might sting a little. Hold onto what the textbook said: a score shows performance against a norm group. It isn't the whole person.

SoheeThat's true of an exam score too. Keep going. We'll see you next time on EPPP Prep.

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